bycatch accounting and steve parker sophie mormede ......sophie mormede stuart hanchet new zealand....
TRANSCRIPT
Bycatch accounting and
management in the
Ross Sea toothfish fishery
Steve ParkerSophie MormedeStuart Hanchet
New Zealand
Ross Sea Region
• 4.5 million km2 of ocean• High seas fishery• Managed by CCAMLR
• Consensus of 25 members
Small-Scale Research Units
(SSRUs)• Open/closed areas• Depth restrictions
• Green =550-1800m
• Regional catch limits
McMurdo
Slope
Shelf < 550 m
Northern seamounts
• Bottom longline only• Started in 1998• ~3200 t annually• Summer only (Dec-Feb)• Deepwater (800-2000 m)• ~20 vessels from 10 nations• Two scientific observers each• Assessed via mark-recapture and
integrated stock assessment
Bycatch species
Habitat forming invertebrates (23 taxa)Seabirds (1 in 2004, 1 in 2013)No penguinsNo marine mammals
3 grenadiers (Macrourus whitsoni, caml, holotrachys)2 skates, (Amblyraja Georgiana, Bathyraja cf. eatoni )1 eelcod (Muraenolepis evseenkoi +?)1 icefish (Chionobathyscus dewitti )1 deep sea cod (Antimora rostrata)Several rock cods (Trematomus sp.)Other minor species (e.g., plunderfish)
Minor bycatch species
Eelcod
Icefish
Plunderfish
Bycatch management
• Article II of the CCAMLR Convention– Target fished population is above a level which ensures stable
recruitment (above 50% virgin biomass for toothfish).
– Ecological relationships between harvested, dependent, & related populations are maintained.
– Prevention of changes in marine ecosystem which are not potentially reversible over 2-3 decades.
• Implemented through annual Conservation Measures agreed through consensus of 25 Members.
Setting catch limits
• Macrourus– By analogy to other areas of Southern Ocean
– Trawl survey extrapolation
– Acoustic survey via fishery (in progress)
• Skates– Percentage of toothfish catch limit
– Tagging program
– Preliminary stock assessment
• Other species– Composite 20 t catch limit (per SSRU)
Bycatch management
• Conservation Measure 33-03– 5 nm move-on rule if any species greater than 1 t per set.– Macrourus
• Catch limit in 88.1 = 430 t.• If the catch of Macrourus spp. taken by a single vessel in two successive 10-day periods in a
single SSRU exceeds 1 500 kg, and exceeds 16% of the catch of toothfish by that vessel, the vessel shall cease fishing in that SSRU for the remainder of the season.
– Skates• 5% of toothfish catch limit by weight (~160 t dead)• All skates and rays must be brought on board to be checked for tags.• All live skates released
• Conservation Measure 41-09– Macrourus catch limit allocation to SSRUs based on historical proportions
• Conservation Measure 22-07 VMEs– Habitat forming organisms, 1 nm radius closures at 10 kg per 1200 m line
segment.
• Conservation Measure 25-02 & 24-02 Seabirds– Streamers, sink rates, weighted lines, BEDs, offal and discard prohibition.
Main bycatch species
Year
Ca
tch
(n
um
be
rs)
0
5000
10000
15000
20000
25000
1997 1999 2001 2003 2005 2007 2009 2011 2013
Skates
Year
Catc
h (
t)
0
100
200
300
400
500
600
1997 1999 2001 2003 2005 2007 2009 2011 2013
Macrourids
Limit
Year
Catc
h (
t)
0
50
100
150
200
250
300
1997 1999 2001 2003 2005 2007 2009 2011 2013
Skates
Limit
Year
Catc
h (
t)
0
10
20
30
40
50
1997 1999 2001 2003 2005 2007 2009 2011 2013
EelcodIcefishMorids
Rock cods
Limit per SSRU
Combined
Spatial distribution of catch
MacrourusRisk factors
– Abundance-based catch limits well above catch
– Population large by comparison with others
– Vulnerable life histories, esp 1 species
– Stable recent CPUE, but active avoidance, gear change
– Ice conditions (and potentially management) could force vessels to fish in high catch rate areas
– Ecologically a key slope demersal species
Skates
Risk factors
– Most released alive– Tagging program uncertainties
• Species identification• Release mortality• Movement patterns
– Species identification issues– Vulnerable and uncertain life histories– Catch limits not biologically based– Declining trend in catch
Other species:
Muraenolepis, Channichthyids,
Antimora, Notothenioids
Risk factors
– Small catches (typically < 5 t)
– Recent declining trends (through 2012), but likely spatially driven
– More productive life histories, but limited information
– Catch limits not biologically based
Three species
spatial population models
Criteria:
• Interaction with toothfish (prey)
• Important (50% of diet)
• Directly impacted via the fishery
• Different life histories
Next most important fish
~ 12% diet
Macrourid Icefish
Toothfish
Building spatial components
• Biomass of prey spatially (using spatial CPUE values)
+ biomass of toothfish spatially (toothfish spatial model)
+ electivity of toothfish (based on stomach contents)
+ residual mortality of prey species
+ fishery removals spatially
+ selectivity of the fishery (derived from observed length)
= spatial model of the three species through time
toothfish macrourid icefish
Estimated spatial temporal trends
Biomasst
Biomass trends and prey switching
Summary• Ross Sea toothfish fishery uses large closed areas, catch
limits, move-on rule, CPUE monitoring to control bycatch.
• Observers provide good monitoring of species catch.
– Skate exception (ID and release mortality)
• Catch is heavily influenced by location, gear type.
• Impacts of fishing on bycatch populations are dependent on:
– Spatial distribution
– Understanding life histories
– Ecosystem response to fishing (direct and indirect)
• Expected interactions with fishery via multi-species spatial
models.
– Useful for designing and assessing monitoring tools for prey species.
– Provide testable hypotheses for system dynamics.
Acknowledgements
• NZ Ministry for Primary Industries
• NZ Ministry for Business, Innovation and Employment
• Alistair Dunn for spatial population model software
• NZ Antarctic Working Group
• CCAMLR
• NZ and CCAMLR Observers